In the U.S. copending application, Ser. No. 547,151 which was filed on Feb. 5, 1975 in the name of Paul Neyraud and is assigned to the assignee of the present invention, machines of the type in question are described which include means for controlling the thread tension, that is the feeding of each thread or group of threads, in such a manner as to permit the making of a boucle fabric, or loop pile fabric, in which the loops are formed with as many as four different loop heights. The described device comprises an assembly of cylinders and a roller capable of being brought into contact to pinch the threads against them for the purpose of imparting to the threads more or less tension. Such systems, although functioning in a perfectly satisfactory manner, are however complex and rather uneconomic.
The improvements which comprise the object of the present invention seek to remedy the drawbacks of the prior art, and to provide a device for feeding thread which is especially useful on tufting machines for making patterned loop pile fabrics, which device performs particularly well by providing various practical advantages.